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ought to be treated in the college of engineering, there is a tendency to attempt too much. The graduate practitioner, who is well grounded in the essentials of engineering construction, should be able to lay hold of and apply the needed data and master the special details when the task is before him.

BIOLOGY FOR CIVIL ENGINEERS.

BY GEORGE C. WHIPPLE,

Brooklyn, N. Y. The civil engineer, in the practice of his profession, makes use chiefly of materials which are lifeless, or, as the chemist would say, inorganic. Iron, stone, sand, brick, cement are inert and almost unchangeable. In dealing with them we may use the rules of mathematics; stresses and strains may be figured and the supporting power of the different materials computed. Mobile substances like water and mercury may likewise be treated from the physical standpoint; their pressure and velocity of flow are ready subjects of calculation. So universal are the applications of physics and mathematics to engineering operations that we are sometimes inclined to forget that the engineer is also concerned with substances which must be treated from a different standpoint.

All engineering work is designed to minister directly or indirectly to the needs of the human being, and therefore, the engineer must be brought more or less into contact with organic matter. This organic living matter is subject to other laws than those of physics ; the subtle laws of chemistry and biology play a most important part and must not be overlooked. The object of this paper is to show the practical bearing which the science of biology has upon engineering and to emphasize its importance in the education of engineering students.

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The word “biology,” used in its broadest signification, means “the science of life,” or, better, "the science of matter in the living state.” Thus regarded it embraces many subdivisions, as botany, zoölogy, physiology, morphology, etc., which, because they treat of phenomena of life, are called “the biological sciences." The word biology is sometimes used in a more limited sense, as treating of the fundamental principles of life, the nature and properties of protoplasm, and the structure of the cell. This “

This “general biology” is often studied by itself as an introduction to botany, zoology and the other biological sciences. Engineers and sanitarians are now using the word biology in a still different sense, applying it to the study of those minute forms of life with which the engineer is concerned and which are more or less closely related to the public health. This division of the subject may be more properly called “sanitary biology” and defined as that branch of biology which treats of the micro-organisms in their relation to the public health. As these micro-organisms include both plants and animals, sanitary biology necessarily encroaches upon the fields of botany and zoology.

We may look best at our subject along two lines, according to the subdivision of the micro-organisms proposed by Professor Sedgwick.

Bacterial Organisms.

Requiring special cultures.

Difficultly studied with

the microscope.
Micro-Organisms.* Microscopic in size.

Plants. Organisms, either plants or animals, invisible or Microscopical Organisms. barely visible to the naked

Not requiring special eye.

culture.

Easily studied with the microscope.

Microscopic in size or slightly larger.

Plants or animals. The methods used in the study of these two classes of organisms vary greatly. The bacteria, by reason of their small size, cannot be examined directly but must be cultivated in suitable media and studied in mass. It is only by using many different media and determining the character of the growth upon each, that one is able to separate the different species. The microscopical organisms, on the other hand, are much larger; they may be studied easily with microscopes of comparatively low powers.

The history of the study of the micro-organisms is an interesting one. It is closely intertwined with the history of the microscope. Every great improvement in that instrument has been followed by new revelations regarding these lowest forms of life. In 1827 the compound microscope was corrected for chromatic

* Wm. T. Sedgwick. Recent progress in Biological Water Analysis. Journal of the New England Water Works Association, September, 1889.

aberration and otherwise perfected. Its newly discovered optical powers were put to use in connection with the study of the “germ theory.” Yeast plants were seen in fermenting solutions and other organisms were observed in various putrefying substances. Little by little it dawned upon the scientific world that the minute organisms, which, at first, were only objects of curiosity, play a most important part in the world's history. Then occurred the hotly contested struggle over the question of "spontaneous generation,” which was not settled definitely until Pasteur, in 1855, performed his celebrated series of experiments. The results of that contest have been far reaching, but not the least important have been the new methods brought out for the study of the bacteria. The use of the cotton air filter, the sterilization by heat, and the employment of solid media (Koch's method) for pure cultures, lie at the very foundation of the new science of bacteriology

Provided with new methods of work and with microscopes of greater perfection, scientists, great and

, small, began the search for bacteria. Earth, air and water were examined. New forms were found on every hand. The scientific magazines teemed with descriptions of bacillus this and bacillus that. In the midst of many observations which had little value except in stimulating inquiry, there were some discoveries that were epoch-making in their importance. It was proved that certain diseases of man and animals were directly caused by certain specific organisms. Koch discovered the bacillus of tuberculosis in 1882 and that of Asiatic cholera in 1884. In the

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